1. Field of the Invention
The present invention relates to a hermetic reciprocal compressor, and more particularly, to a connecting-rod apparatus of a hermetic reciprocal compressor, which connects a crankshaft and a piston.
2. Description of the Prior Art
A conventional hermetic compressor includes a motor unit having a stator and a rotor rotatably installed next to the stator, a crankshaft, a connecting-rod, and a piston.
The crankshaft is integrally rotated with the rotor that is connected to the crankshaft, and has an eccentric portion at a lower part. The eccentric portion is connected with a large diameter portion formed at one end of the connecting-rod. The piston is connected with a small diameter portion disposed at the other end of the connecting-rod. The piston reciprocally moves in a piston chamber of a cylinder.
In the above structure, the crankshaft is rotated along with the rotor so that the eccentric portion can be rotated. The connecting-rod converts the eccentric rotation of the eccentric portion to linear movement to allow the piston to reciprocally move.
In the meantime, in the hermetic compressor having the above structure, the angle of the axis of the crankshaft and the connecting-rod is a right angle, and the angle is known as a very important mechanical element in designing. Therefore, a forming tolerance is generally written on related elements.
In addition, the piston slides maintaining appropriate clearance in the piston chamber of the cylinder. Yet, the parallelism and the symmetry of the piston with respect to the axis should be maintained constant.
Moreover, the angle of the piston and a piston pin is a right angle. For the connecting-rod, the parallelism and the symmetry of the large diameter portion and the small diameter portion are very important elements.
As described so far, the arrangement of the connecting-rod to the axis of the crankshaft, that is the various mechanical connection relationships based on the connecting-rod is a crucial element in driving the compressor. Therefore, when the arrangement of the connecting-rod to the axis of the crankshaft is not stable, there is friction and abrasion for each element of the compressor. Consequently, the compressor might not be able to drive normally. Especially, when the crankshaft and the piston are not mechanically arrayed, the above problem can be aggravated.
Considering the above problem, an apparatus to compensate the misalignment of the axis of the crankshaft and the axis of the piston has been disclosed in U.S. Pat. No. 6,164,188. In other words, a compressor having a piston-rod connected with a cylinder at one end and a round concave portion at the other end, an alignment adaptor having a concave portion corresponding to the above concave portion at one end and fixed with the piston-rod by using a bolt, a ball inserted between the above two concave portions, and an expansion-rod fixed and connected with the alignment adaptor and a clamp is disclosed therein. According to the above structure, the ball is inserted between the piston-rod and the alignment adaptor. Thus, the ball can move freely, and mis-alignment is effectively compensated. However, to insert the ball, an additional alignment adaptor and a clamp are required. Therefore, there is a problem that the compressor needs a lot of parts and the structure of the compressor is complicated. Consequently, the productivity is decreased.
Furthermore, another compressor including a connecting-rod body having a small end portion to embrace a piston pin and an integrally formed pork portion with a connection hole at the other end, a bushing having a pair of protrusions to be connected with the connection hole, an insert hole for embracing a crank pin, and an elastic clip to fix the body and the bushing is also disclosed. However, in this case, the connecting-rod body and the bushing are connected with each other by the elastic clip, thus there is a limitation in movement and noise is generated due to friction and the abrasion.
The present invention has been made to overcome the above-mentioned problem of the prior art. Accordingly, it is the object of the present invention to provide a connecting apparatus of a hermetic reciprocal compressor having an improved structure to reduce abrasion and noise.
The above object of the present invention is realized by providing a connecting apparatus of a hermetic reciprocal compressor to convert a rotary movement into a reciprocal sliding movement by connecting an eccentric portion of a crankshaft and a piston according to the present invention, including a ball; a first connecting member having a small diameter portion connected with a piston pin being connected with the piston, and a connection portion extended from the small diameter portion, wherein the connection portion has a ball embracing surface to embrace the ball and supports the ball to be moved; a second connecting member having a large diameter portion rotatably connected with the eccentric portion, and an extending yoke portion at an outside of the large diameter portion, which supports the ball against the embracing surface and prevents the ball from being separated; and a third connecting member to connect the first connecting member and the second connecting member such that the first connecting member an the second connecting member relatively move with the ball placed therebetween.
The ball embracing surface is penetrated from an upper side and an end side of an end portion of the connection portion for a predetermined depth.
The yoke portion is extended from an outside of the large diameter portion in order to face the ball embracing surface, and includes a vertical side and a sloping side formed with respect to a vertical direction to allow the ball to be contacted, and wherein the vertical side and the sloping side are formed as an arc shape in a horizontal direction.
When the first connecting member and the second connecting member are connected, a predetermined flexible gap is defined between an end portion of the connection portion and an outside of the large diameter portion so that the first connecting member and the second connecting member can be relatively rotated.
The flexible gap is between 0.2 mm to about 0.5 mm.
The third connecting member is preferably a metal wire to secure or clamp by wrapping the wire around the large diameter portion and the connection portion.
The first connecting member has an oil passage that penetrates in an upper side of the connection portion and is connected with the small diameter portion, and an oil dropping from the yoke portion of the second connecting member is supplied to the small diameter portion through the oil passage.